html {
  height: 100%;
}

body {
  margin: 0;
  height: 100%;
  background: url("../images/bg.jpg") no-repeat;
  background-size: 100% 100%;
}

#drum-kit {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 95%;
  height: 360px;
}

.kit {
  font-size: 5em;
  font-family: Georgia, 'Times New Roman', Times, serif;
  text-align: center;
  color: #ffffff;
  width: 120px;
  height: 120px;
  line-height: 120px;
  background-color:rgba(0, 0, 0, 0.3);
  box-shadow: 0px 0px 5px 5px #000000;  /*参数分别为：x偏移量，y偏移量，模糊度，扩散度，颜色*/
  /* filter: blur(2px); */
}

.playing {
  transform: scale(1.1);
  box-shadow: 0px 0px 5px 5px red;
  transition: all 0.1s;
}